Electric and electronic devices such as personal computers and telephone sets are increasingly provided as mobile devices. The parts constituting these devices are required to have a small size, light weight and thin wall and such mechanical properties as high strength and high stiffness. It is especially necessary that the housings of these devices do not bend at least partially to contact inside parts for breaking the inside parts or to break themselves in the case where external loads act on the housings.
JP 2006-044259 A (Patent Literature 1) proposes a molded article for forming a housing. This molded article is an integrally molded article that uses a laminated member comprising numerous continuous reinforcing fibers arranged in one direction and a thermosetting resin (plate member) as a ceiling plate of the housing, wherein the ceiling plate is integrally bonded onto the top faces of the side frames formed of a thermoplastic resin including reinforcing fibers (resin member) of the housing by a thermoplastic resin composition (adhesive). This integrally molded article has an advantage that sufficient adhesion can be obtained between the ceiling plate and the side frames. However, the joints between the ceiling plate and the side frames are positioned on the top faces of the side frames, that is, the ceiling plate overlaps on the side frames, to form the joints. Therefore, the thickness of the ceiling plate at the joints prevents the housing from having a thin wall.
JP 2007-038519 A (Patent Literature 2) proposes a molded composite article for forming a housing. The molded composite article comprises a plate member and a resin member, wherein the plate member and the resin member are integrally bonded to each other at side end faces thereof facing each other. The plate member has a three-layer structure comprising an upper layer, a lower layer and a core layer positioned between the upper and lower layers. That is, in this case, the molded composite article has a sandwich structure in which the core layer is kept between the upper and lower layers. The core layer is a soft member (for example, a foamed material), and the upper and lower layers are hard members (for example, a resin including reinforcing fibers). This molded composite article is produced by injection-molding a resin forming the resin member toward a side end face of the plate member. The resin injected by the injection molding partially penetrates like a projection into the core layer from the side end face of the core layer, to bond the plate member and the resin member to each other.
This molded composite article is free from joint at which the plate member and the resin member overlap on each other, and the joint between both the members are positioned between side end faces of both the members, to allow the wall thickness of the housing to be reduced. However, in the case where the resin flowability is low during injection molding or in the case where a high injection pressure is not available, the projection-like penetration of the resin member into the core layer is insufficient, and it is difficult to obtain a sufficient bonding strength between the plate member and the resin member. Further, in this publicly known housing, the joint line between the side end face of the plate member and the side end face of the resin member are straight lines. Therefore, stress concentration is likely to occur at the joint, and for this reason, it is difficult to obtain a sufficient bonding strength.
As described above, there still remains a demand for a technique that allows a wall thickness of a housing to be reduced and that can achieve a sufficient bonding strength between both the members.    Patent Literature 1: JP 2006-044259 A    Patent Literature 2: JP 2007-038519 A